The present invention relates to a laminate optic with an interior Fresnel lens, and more particularly to an artificial composite intraocular lens for insertion into an eye through a corneal incision of minimal size, having a partially hollow laminate optic of flexible, temporarily deformable material, including a pair of opposed interior surfaces, at least one of which is formed as a protected internal Fresnel lens, and both of which together define captive gas spaces therebetween.
For treatment of conditions such as natural eye lens cataracts, a known eye surgery procedure is to remove the cataracted lens through an incision in the wall of the cornea of the eyeball, and replace it by an artificial intraocular lens as an internal implant lens. Intraocular lenses are often made of flexible material such as silicone plastic to permit reduction of their overall apparent girth by temporary deformation for facilitating their insertion through the cornea, thereby advantageously enabling use of a corneal incision of concomitantly reduced size.
Such intraocular lenses often have haptics extending from the periphery of their optics, i.e. normally expanded resilient appendages connected to the central lens body or optic, to aid lens seating in the eye. Preferably, these haptics should also be kept in contracted state during insertion of the lens into the eye to enable the lens unit to fit without difficulty through a minimum size incision.
U.S. Pat. No. 4,573,998 to Mazzocco and U.S. Pat. No. 4,534,069 to Kelman are among typical proposals offered to provide the flexible optic and/or haptics of such an intraocular lens in temporarily reduced girth condition for incision insertion purposes.
However, known optics of flexible material, such as silicone rubber or plastic, have the distinct drawback that in order to achieve the desired optical characteristics of the particular intraocular lens, the optic must be made relatively thick, as measured along the optical axis, thereby increasing its mass and volume.
Consequently, the sought advantage of forming the optic of flexible material, e.g. providing a silicone optic, which would otherwise permit the optic to be deformed by curling, folding or the like, into a generally cylindrical shape of sufficiently small apparent girth to fit through a minimum length corneal incision, cannot be achieved. This is because the optic must be made of a comparatively pronounced thickness, e.g. 3 mm, for purely optical reasons, and therefore is of such mass and volume that it cannot readily be curled, folded, etc. into a small enough generally cylindrical shape to accomplish the underlying purpose of forming the optic of flexible material, i.e. to exploit the use of a minimum size incision.
A Fresnel lens is a known type of lens which is greatly reduced in weight by dividing the continuous lens surface into a succession of concentric rings, assembled in correct relationship on a generally flat surface. More specifically, it is a compound lens of annular prisms, providing a stepped lens of less weight and thickness than, for example, a corresponding plano-convex lens, with the risers of the steps desirably set at such an angle as to present no disturbance to the light rays. An advantage of such a Fresnel lens is that its collection angle is generally much greater than practicable for a solid type, e.g. plano-spheric, lens.
U.S. Pat. No. 4,673,406 to Schlegel is a recent proposal concerning the inclusion of an exterior Fresnel lens formation on the deformable lens body or optic of an artificial intraocular lens, made of a homogeneous, crystal-clear, high-temperature resistant plastic, preferably vulcanized silicone, to enhance the optical characteristics of the system while reducing the optic thickness. Specifically, the exterior Fresnel lens formation is configured with a circular central portion and at least one annular portion immediately surrounding and backwardly offset from the central portion to reduce the thickness of the lens body and facilitate its folding during lens implantation into the eye. However, once inserted in the eye, the surrounding aqueous humor in the eye interior coats the exterior Fresnel lens formation and detracts from the optical effectiveness thereof, since the aqueous humor has an index of refraction sufficiently close to the index of refraction of the intraocular lens material that the optical characteristics of the Fresnel lens are detrimentally offset.
It would be desirable to provide a deformable intraocular lens for insertion into the eye to achieve the above noted overall advantages, especially the use of a minimum size corneal incision, yet which has a Fresnel lens formation which is protected from the adverse effects on its optical characteristics of the aqueous humor environment inside the eye.